A red light-emitting material is indispensable as an important component of the three primary colours, red, green and blue. Red light-emitting materials broadly applied at present include Y2O3:Eu3+(Bi3+), Y2O2S:Eu3+(Bi3+), Y(V,P)O4:Eu3+(Bi3+), (Y,Gd)BO3:Eu3+ and (Ca,Sr)S:Eu2+(Tm3+) etc. However, as traditional technologies, including display and illumination etc., have been changed, these traditional red light-emitting materials, which used to be radiant, fail to well meet the needs of the development of new technologies, including three-dimensional (3D) display and white Light-Emitting Diodes (LED) etc., because of changes in application fields and excitation modes.
Since the late 1990s, a category of novel nitrogen/nitrogen oxide light-emitting materials have been developed. Anionic groups of the light-emitting materials of this category contain high negative charge N3−, and excitation spectra of the light-emitting materials move towards longer wavelengths including near ultraviolet and visible light etc. because of the expansion effect of electronic cloud. In addition, substrates of the light-emitting materials are provided with relatively dense network structures having stable physicochemical properties.
A kind of MxSiyNz:Eu (M is at least one of Ca/Sr/Ba, and z=2/3x+4/3y) red light-emitting nitride material was disclosed in a patent document EP1104799A1 in 2001, and representative red light-emitting materials mainly include three materials, i.e. MSiN2:Eu, M2Si5N8:Eu and MSi7N10:Eu, and the like. It is reported in a non-patent document Chem. Mater. 2006, 18: 5578 that the light-emitting intensity of this kind of Sr2Si5N8:Eu red light-emitting nitride material at 150□ is only 86% of that at room temperature.
A kind of MaAbDcEdXe red light-emitting material is invented in a Chinese disclosure patent ZL 200480040967.7. In the formula, a+b=1, and M is one or two elements of Mn/Ce/Pr/Nd/Sm/Eu/Tb/Dy/Ho/Er/Tm/Yb, A is one or two elements of Mg/Ca/Sr/Ba, D is one or two elements of Si/Ge/Sn/Ti/Zr/Hf, E is one or two elements of B/Al/Ga/In/Sc/Y/La/Ga/Lu, and X is selected from one or two elements of O, N and F. The inorganic compound has the same crystal structure as that of CaAlSiN3, and 0.00001≦a≦0.1, 0.5≦c≦4, 0.5≦d≦8, 0.8*(2/3+4/3*c+d)≦e and e≦1.2(2/3+4/3*c+d), wherein a typical composition is CaAlSiN3:Eu. It is reported in a non-patent document Sci. Technol. Adv. Mat., 2007, 8(7-8): 588-600 that the light-emitting intensity of this kind of CaAlSiN3 light-emitting material at 150□ is 89% of that at room temperature, which is higher than that of the Sr2Si5N8:Eu light-emitting material.
A certain amount of Aluminium Nitride (AlN) was introduced based on CaSiN2:Eu in a non-patent document (Int. J. Appl. Ceram. Technol., 2010, 7(6):787-802) in 2009 to obtain Cal-xAlzSiN2+z:Eux (0<z<0.3). However, with the introduction of AlN, the light-emitting efficiency of the material is reduced significantly. The external quantum efficiencies of the material excited at 405 nm and 450 nm are only 28.5% and 24.5%, respectively. In addition, it is reported by the document that, Ca0.999SiN2:EU0.001, with a relatively low thermal quenching temperature at about 110□, has bad temperature properties.
The red fluorescent powder involved in the documents above has better temperature properties than those of traditional red sulfide fluorescent powder ((Ca,Sr)S:Eu2+). At the same time, it can be easily learned that the light-emitting intensities of the red light-emitting materials involved in the documents above at 150□ are all lower than 90% of those at room temperature, which remains to be improved. In addition, red light-emitting materials applied in devices to efficiently improve colour rendering indexes are required to have wide half widths while the light-emitting half widths of the light-emitting materials above are generally about 90 nm which is required to be further widened. In addition, although a high colour rendering index can be obtained by a technical solution which improves the colour rendering index by adding a red light-emitting material, the overall light-emitting efficiency of a device is greatly reduced at the same time, which needs to be alleviated by further improving the light-emitting efficiency of the red light-emitting material.